In the aftermath of Monday's "Day Without Immigrants," the urgent question immigrants and their supporters face is how to translate the passion of the streets into lasting political gains.

In coming months, immigrant rights organizers say, they will shift their energy into making a difference at the polls through registering voters, helping legal immigrants become citizens and getting out the vote in June primary elections around the nation.

"This is only the beginning," said Hilda Delgado of Local 1877 of the Service Employees International Union in Los Angeles. "Now we have to reroute all of the energy and momentum and start registering to vote to send a clear message (for immigration reform) to the Senate and House in Washington."

Organizers have their work cut out for them. According to the Pew Hispanic Center, only 39 percent of the nation's 41 million Latinos are eligible to vote - compared with 76 percent for whites and 65 percent for blacks. And less than half of the 16 million eligible Latino voters actually voted in the 2004 general election. Pew center director Roberto Suro said Latinos must now convince the broader public that legislation expanding guest worker programs and offering undocumented immigrants a chance to legalize would be good for the nation.

That message, however, will be fought by immigration control advocates, who say the past two months of marches and rallies have drawn new recruits to their cause of cracking down on illegal immigration.

Since the March 25 Los Angeles march startled the nation by drawing 500,000 people into the streets, the Phoenix-based Minuteman Civil Defense Corps, which monitors the nation's borders, has significantly increased its volunteers, fundraising and Web site traffic, said spokeswoman Connie Hair.

She said 400 new volunteers joined the group in the first week after the L.A. march, compared with a normal weekly flow of about 135. An Internet appeal for support to begin building private fences on private land along the U.S.-Mexican border raised $150,000 in a week. The group's Web traffic has quadrupled to 36,000 hits per day, she said.

"(The marches) have focused the American people's attention on people marching in the streets and waving Mexican flags ... who may not be grateful for the taxpayer-subsidized benefits they're getting and who are jumping in line ahead of those who are doing it legally," Hair said. "There is a quiet rage building."

In Washington, where the Senate may resume debate on an immigration bill as early as next week, a few congressional officials said the demonstrations would serve to keep the issue on the agenda. But most lawmakers warned that the rallies could polarize the public, make it harder for Congress to negotiate the thorny issue and create a backlash against immigrants - on the Hill and off.